1. Field of the Invention
The present invention relates to a method of location registration, a location registration system, a mobile communication terminal, an equipment for setting up location registration area, program for setting up location registration area, and more specifically to setting up a location registration area (also referred to as a location area) of a mobile communication terminal in a mobile communication system.
2. Description of the Related Art
In the conventional mobile communication system, the location of a mobile communication terminal not in communications is managed by location registration area formed by a plurality of cells. In the conventional mobile communication system, a location registration area is fixedly set beforehand in a network, and is unified for all terminals.
Generally, a change of a location registration area is triggered by a mobile communication terminal not in communications exiting an old location registration area and entering a new location registration area. When the terminal detects a change of location registration area identification information advertised by a base station, it notifies the network of the change, and the location registration area information about the mobile communication terminal is changed in the network. When a communication request for the terminal not in communications occurs, paging (general call) request signals are transmitted to all cells in the location registration area of the terminal in the network. Then, upon receipt of the paging request, the terminal returns a paging response to the network. Thus, the network can be informed of the cell (base station in the network) in which the terminal is located.
Assume that the optimum location registration area obtains the minimum sum of the location registration traffic of the terminal and the paging traffic. Then, the optimum location registration area depends on the mobility and traffic characteristics of the terminal. Therefore, the optimum location registration area generally different for each terminal. Furthermore, the mobility and traffic characteristics of the terminal change with time, the optimum location registration area for one terminal also changes with time.
Therefore, conventional method of the location management which uses the unified and fixed location registration area is inefficient. That is, in the conventional method, for example, the location management is performed in the same location registration area for a static mobile communication terminal and a mobile communication terminal which frequently changes its location registration area. Therefore, a wasteful traffic can arise when the location registration and paging operation are performed. Namely, the conventional method is insufficient.
The technology for solving the above mentioned problems can be, for example, in Japanese Unexamined Publication No. Heisei 7-322333. As a method of setting up a location registration area for each mobile communication terminal, this publication discloses a method of the mobile communication terminal computing and setting up the optimum location registration area, and a method of the base station computing and setting up the optimum location registration area.
However, the location registration system in the method disclosed in the above mentioned publication pays attention only to the traffic in the radio region, and the traffic in the mobile communication network is not considered.
Furthermore, in the location registration system in the method disclosed by the above mentioned publication, the mobile communication terminal or the base station determines a location area. Thus, there can be a problem with the traffic which the size information about peripheral cells required in setting up a location area is computed.
That is, an area of a peripheral cell is a piece of the information used in setting up the optimum location registration area. However, in the current system, an area of a cell is set up based on the predicted number of subscribers, and therefore depends on the location. For example, the areas of cells are different between a downtown area and a suburban area. Therefore, in the method of the above mentioned publication, it is necessary to obtain the size information about the peripheral cells when the mobile communication terminal computes the optimum location registration area, and there can be a problem with the traffic therewith.
The present invention has been developed to solve the problems with the above mentioned conventional technology. And an object of the present invention is to provide a location registration method, a location registration system, a mobile communication terminal, a location area setting equipment, and a location area setting program which are capable of realizing efficient location management of the mobile communication terminal with reduced traffic.